Faruk Orman, who spent 12 years in prison for murder after his own lawyer encouraged a key gangland witness to give evidence against him, is suing Victoria Police for unspecified damages, alleging the force "falsely imprisoned" him.

Mr Orman, whose conviction was quashed last year because of the Lawyer X scandal, has filed a writ in the Supreme Court, claiming more than a dozen major failings by the police force.

He is accusing police of breaching their duty of care to him, failing to properly supervise, control or train their officers and "maliciously" prosecuting him.

"As a consequence of the above, the plaintiff has suffered injury, loss and damage," the writ said.

Mr Orman is seeking unspecified damages, interest and costs but the suit, if successful, could leave Victoria Police on the hook for millions of dollars as it continues to grapple with the fallout from using criminal barrister Nicola Gobbo as a human source.

Her role in Melbourne's bloody gangland war has sparked not only a dramatic television series but a royal commission which is currently probing how her informing ultimately brought the Victorian justice system to its knees.

Among Ms Gobbo's most notorious clients were underworld figures Tony Mokbel and slain kingpin Carl Williams.

She also represented Mr Orman, who was jailed for the murder of another underworld figure, Victor Peirce, who was shot dead in his car in 2002.

Mr Orman was found guilty of being the getaway driver and was sentenced to 20 years in prison, but has long professed his innocence, and appealed his conviction to Australia's High Court.

But after 12 years in jail, and as news of Ms Gobbo's relationship with police became public, Mr Orman's conviction was quashed by Victoria's Court of Appeal.

The court heard that even though Ms Gobbo was representing Mr Orman, she also encouraged a key witness to give evidence against him at trial.

The President of the Court of Appeal, Chris Maxwell, said Ms Gobbo's actions were a fundamental breach of her legal obligations to her client and to the court.

"On the facts conceded, Ms Gobbo's conduct subverted Mr Orman's right to a fair trial and went to the very foundation of the system of criminal trial," he said.

Mr Orman's acquittal and Ms Gobbo's extreme fall from grace has left some key underworld figures hopeful that their convictions will also be overturned, which could signal a wave of compensation claims against Victoria Police.

Meanwhile, the force is anxiously awaiting the outcome of the royal commission.

The commission was due to issue its final report on July 1, but on Tuesday revealed it had requested an extension, partly because it has to review the cases of more than 1,200 people who may have been potentially affected by Ms Gobbo's use as a police informant.

It will now hand down its final report on November 30, 2020.

Victoria Police said it would not be commenting as the matter was before the courts.